A gear unit for a manipulator can comprise three segments mounted following each other and pivotable together with respect to each other about first and second inclined pivot axes with three drive shafts mounted concentric to each other, of which intermediate drive shafts are journaled along the first and second inclined pivot axes and which can have reduction gears associated with their output or driven side. The first and second inclined pivot axes form acute angles with the longitudinal axis of the manipulator arm, being inclined in opposite directions in the extended configuration of the arm.
German printed patent application DE-AS No. 27 45 932 described a gear unit for a manipulator having two segments mounted following each other which are pivotally mounted in planes inclined to each other. The tool holder on the rear gear segment is rotatably mounted on a pivot axis coaxial with the main drive shaft axis of the manipulator.
In the extended configuration of this manipulator gear head there are problems with the computationally controlled motion of the manipulator. A rotation predetermined by computer program of the tool held by the rear segment about the second inclined rotation axis is clearly allowed during computer control, if the gear unit is rotated about the axis of the concentric main drive shaft or if the rear segment is alone rotated about this axis. This ambiguity causes negative effects in continuous path control and up to now could only be overcome by programmed and/or control engineering manipulations to be sure unsatisfactorily. With point to point control the coaxial arrangement of the second inclined pivot axis with the concentric drive shaft is not a problem.
In German Open Patent Application DE-OS No. 34 28 748 three gear unit segments connected in cascade comprise the gear head unit for the manipulator. The intermediate or middle gear-head segment has two inclined pivot axes which form acute angles with the longitudinal axis of the gear head unit inclined in opposite directions. At the end of the intermediate gear shaft leading to this gear-head segment at least one large reduction gearing unit is mounted.
In one example, this gear-head unit has a substantially larger motion play in a compact structure. As a consequence of the inclined pivotability of the rear segment with respect to the intermediate segment an essentially larger operating range for the tool held by the manipulator is attained. Since, in this case, the output drive shaft is not coaxial with the main drive shaft the ambiguity in the calculational control is avoided.